.part .l3 {
    display: block;
    width: 400px;
    margin: 0 auto;
}

.part ul {
    display: flex;
    flex-flow: row wrap;
    justify-content: space-between;
}

.part ul li {
    /*项目不放大不缩小 固定单位*/
    flex: 0 0 170px;
    text-align: center;
    border: 1px solid black;
    margin-bottom: 10px;
}

.part ul li img {
    width: 120px;
}